This application claims the benefit under 35 U.S.C. xc2xa7 119 (a)-(d) of United Kingdom Application No. GB 0216571.0, filed Jul. 17, 2002, which is incorporated herein by reference in its entirety.
This invention relates to a number of phenylalanine enamide esters, to compositions containing them, to processes for their preparation, and to their use in medicine.
Over the last few years it has become increasingly clear that the physical interaction of inflammatory leukocytes with each other and other cells of the body plays an important role in regulating immune and inflammatory responses [Springer, T. A., Nature, 346, 425, (1990); Springer, T. A., Cell, 76, 301, (1994)]. Specific cell surface molecules collectively referred to as cell adhesion molecules mediate many of these interactions.
The adhesion molecules have been sub-divided into different groups on the basis of their structure. One family of adhesion molecules which is believed to play a particularly important role in regulating immune and inflammatory responses is the integrin family. This family of cell surface glycoproteins has a typical non-covalently linked heterodimer structure. At least 16 different integrin alpha chains and 8 different integrin beta chains have been identified [Newman, P. et al, Molecular Medicine Today, 304, (1996)]. The members of the family are typically named according to their heterodimer composition although trivial nomenclature is widespread in the field. Thus the integrin xcex14xcex21 consists of the integrin alpha 4 chain associated with the integrin beta 1 chain, but is also widely referred to as Very Late Antigen 4 or VLA-4. Not all of the potential pairings of integrin alpha and beta chains have yet been observed in nature and the integrin family has been subdivided into a number of subgroups based on the pairings that have been recognised to date [Sonnenberg, A., Current Topics in Microbiology and Immunology, 184, 7, (1993)].
The importance of integrin function in normal physiological responses is highlighted by two human deficiency diseases in which integrin function is defective. Thus in the disease termed Leukocyte Adhesion Deficiency (LAD) there is a defect in one of the families of integrins expressed on leukocytes [Marlin, S. D. et al, J. Exp. Med. 164, 855, (1986)]. Patients suffering from this disease have a reduced ability to recruit leukocytes to inflammatory sites and suffer recurrent infections, which in extreme cases may be fatal. In the case of patients suffering from the disease termed Glanzman""s thrombasthenia (a defect in a member of the beta 3 integrin family) there is a defect in blood clotting (Hodivala-Dilke, K. M., J. Clin. Invest. 103, 229, (1999)].
The potential to modify integrin function in such a way as to beneficially modulate cell adhesion has been extensively investigated in animal models using specific antibodies and peptides that block various functions of these molecules [e.g. Issekutz, T. B., J. Immunol. 149, 3394, (1992); Li, Z. et al, Am. J. Physiol. 263, L723, (1992); Mitjans, F. et al, J. Cell Sci. 108, 2825, (1995); Brooks, P. C. et al, J. Clin. Invest. 96, 1815, (1995); Binns, R. M. et al, J. Immunol. 157, 4094, (1996); Hammes, H.-P. et al, Nature Medicine 2, 529, (1996); Srivata, S. et al, Cardiovascular Res. 36, 408 (1997)]. In particular an anti xcex14xcex27-antibody has demonstrated both clinical and histologic improvement of inflammatory activity and disease in a non-human primate model of inflammatory bowel disease [Hesterberg, P. E. et al, Gastroenterol, 111, 1373-80 (1996)]. A number of monoclonal antibodies which block integrin function are currently being investigated for their therapeutic potential in human disease, and one, ReoPro, a chimeric antibody against the platelet integrin xcex1llbxcex23 is in use as a potent anti-thrombotic agent for use in patients with cardiovascular complications following coronary angioplasty.
Integrins recognize both cell surface and extracellular matrix ligands, and ligand specificity is determined by the particular alpha-beta subunit combination of the molecule [Newman, P., ibid]. One particular integrin subgroup of interest involves the xcex14 chain which can pair with two different beta chains xcex21 and xcex27 [Sonnenberg, A., ibid]. The xcex14xcex21 pairing occurs on many circulating leukocytes (for example lymphocytes, monocytes, eosinophils and basophils) although it is absent or only present at low levels on circulating neutrophils. xcex14xcex21 binds to an adhesion molecule (Vascular Cell Adhesion Molecule-1 also known as VCAM-1) frequently up-regulated on endothelial cells at sites of inflammation [Osborne, L., Cell, 62, 3, (1990)]. The molecule has also been shown to bind to at least three sites in the matrix molecule fibronectin [Humphries, M. J. et al, Ciba Foundation Symposium, 189, 177, (1995)]. Based on data obtained with monoclonal antibodies in animal models it is believed that the interaction between xcex14xcex21 and ligands on other cells and the extracellular matrix plays an important role in leukocyte migration and activation [Yednock, T. A. et al, Nature, 356, 63, (1992); Podolsky, D. K. et al, J. Clin. Invest. 92, 372, (1993); Abraham, W. M. et al, J. Clin. Invest. 93, 776, (1994)].
The integrin generated by the pairing of xcex14 and xcex27 has been termed LPAM-1 [Holzmann, B. and Weissman, I. L., EMBO J. 8, 1735, (1989)]. The xcex14xcex27 pairing is expressed on certain sub-populations of T and B lymphocytes and on eosinophils [Erie, D. J. et al, J. Immunol. 153, 517 (1994)]. Like xcex14xcex21,xcex14xcex27 binds to VCAM-1 and fibronectin. In addition, xcex14xcex27 binds to an adhesion molecule believed to be involved in the homing of leukocytes to mucosal tissue such as gastrointestinal mucosa termed MAdCAM-1 [Berlin, C. et al, Cell, 74, 185, (1993)]. MAdCAM-1 is preferentially expressed in the gastrointestinal track. The interaction between xcex14xcex27 and MAdCAM-1 may also be important at sites of inflammation outside of mucosal tissue [Yang, X.-D. et al, PNAS, 91, 12604, (1994)].
Regions of the peptide sequence recognized by ⊕4xcex21 and xcex14xcex27 when they bind to their ligands have been identified. xcex14xcex21 seems to recognise LDV, IDA or REDV peptide sequences in fibronectin and a QIDSP sequence in VCAM-1 [Humphries, M. J. et al, ibid] whilst xcex14xcex27 recognises a LDT sequence in MAdCAM-1 [Birskin, M. J. et al, J. Immunol. 156, 719, (1996)]. There have been several reports of inhibitors of these interactions being designed from modifications of these short peptide sequences [Cardarelli, P. M. et al, J. Biol. Chem., 269, 18668, (1994); Shorff, H. N.et al, Biorganic Med. Chem. Lett., 6, 2495, (1996); Vanderslice, P. et al, J. Immunol., 158, 1710, (1997)]. It has also been reported that a short peptide sequence derived from the xcex14xcex21 binding site in fibronectin can inhibit a contact hypersensitivity reaction in a trinitrochlorobenzene sensitised mouse [Ferguson, T. A., et al, PNAS, 88, 8072, (1991)].
Since the alpha 4 subgroup of integrins are predominantly expressed on leukocytes their inhibition can be expected to be beneficial in a number of immune or inflammatory disease states. However, because of the ubiquitous distribution and wide range of functions performed by other members of the integrin family it is important to be able to identify selective inhibitors of the alpha 4 subgroup.
We have now found a number of esters which are potent and selective inhibitors of xcex14 integrins. The compounds are able to inhibit xcex14 integrins such as xcex14xcex21 and/or xcex14xcex27, in for example cellular assays such as those described herein, at concentrations at which they generally have no or minimal inhibitory action on xcex1 integrins of other subgroups.
Thus according to one aspect of the invention we provide a compound of formula (1): 
wherein R1 is a xe2x80x94CH(CH3)2, xe2x80x94(CH2)2CH3, xe2x80x94CH2C(CH3)3, xe2x80x94CH2CH2OH, xe2x80x94CH2CH2OCH3, xe2x80x94CH2CH2OCH2CH2OH, xe2x80x94CH2CH2OCH2CH2OCH3, 
group; and the salts, solvates and N-oxides thereof.
It will be appreciated that compounds of formula (1) may exist as enantiomers or diastereomers. The invention is to be understood to extend to all such enantiomers, diastereomers and mixtures thereof, including racemates. Formula (1) is intended to represent all individual isomers and mixtures thereof, unless stated or shown otherwise.
Salts of compounds of the invention include pharmaceutically acceptable salts, for example acid addition salts derived from inorganic or organic acids.
Acid addition salts include hydrochlorides, hydrobromides, hydroiodides, alkylsulphonates, e.g. methanesulphonates, ethanesulphonates, or isothionates, arylsulphonates, e.g. p-toluenesulphonates, besylates or napsylates, phosphates, sulphates, hydrogen sulphates, acetates, trifluoroacetates, propionates, citrates, maleates, fumarates, malonates, succinates, lactates, oxalates, tartrates and benzoates.
Particularly useful salts of compounds according to the invention include pharmaceutically acceptable salts, especially acid addition pharmaceutically acceptable salts.
The compounds of the invention are:
propyl (2S)-2-(2-bromo-3-oxospiro[3.5]non-1-en-1-ylamino)-3-[4-([2,7]naphthyridin-1-ylamino)phenyl]propanoate and the salts, solvates and N-oxides thereof;
2,2-dimethylpropyl (2S)-2-(2-bromo-3-oxospiro[3.5]non-1-en-1-ylamino)-3-[4-([2,7]naphthyridin-1-ylamino)phenyl]propanoate and the salts, solvates and N-oxides thereof;
2-methoxyethyl (2S)-2-(2-bromo-3-oxospiro[3.5]non-1-en-1-ylamino)-3-[4-([2,7]naphthyridin-1-ylamino)phenyl]propanoate and the salts, solvates and N-oxides thereof;
2-(2-hydroxyethoxy)ethyl (2S)-2-(2-bromo-3-oxospiro[3.5]non-1-en-1-ylamino)-3-[4-([2,7]naphthyridin-1-ylamino)phenyl]propanoate and the salts, solvates and N-oxides thereof;
2-(2-methoxyethoxy)ethyl (2S)-2-(2-bromo-3-oxospiro[3.5]non-1-en-1-ylamino)-3-[4-([2,7]naphthyridin-1-ylamino)phenyl]propanoate and the salts, solvates and N-oxides thereof;
2-(morpholin-4-yl)ethyl (2S)-2-(2-bromo-3-oxospiro[3.5]non-1-en-1 -ylamino)-3-[4-([2,7]naphthyridin-1-ylamino)phenyl]propanoate and the salts, solvates and N-oxides thereof;
2-(4-methylpiperazin-1-yl)ethyl (2S)-2-(2-bromo-3-oxospiro[3.5]non-1-en-1-ylamino)-3-[4-([2,7]naphthyridin-1-ylamino)phenyl]propanoate and the salts, solvates and N-oxides thereof;
tetrahydrofuran-2-ylmethyl (2S)-2-(2-bromo-3-oxospiro[3.5]non-1-en-1-ylamino)-3-[4-([2,7]naphthyridin-1-ylamino)phenyl]propanoate and the salts, solvates and N-oxides thereof;
And more particularly:
2-hydroxyethyl (2S)-2-(2-bromo-3-oxospiro[3.5]non-1-en-1-ylamino)-3-[4-([2,7]naphthyridin-1-ylamino)phenyl]propanoate and the salts, solvates and N-oxides thereof;
isopropyl (2S)-2-(2-bromo-3-oxospiro[3.5]non-1-en-1-ylamino)-3-[4-([2,7]naphthyridin-1-ylamino)phenyl]propanoate and the salts, solvates and N-oxides thereof.
The compounds according to the invention are potent and selective inhibitors of xcex14 integrins. The ability of the compounds to act in this way may be simply determined by employing tests such as the cellular assays described in the Examples hereinafter.
The compounds are of use in modulating cell adhesion and in particular are of use in the prophylaxis and treatment of diseases or disorders including inflammation in which the extravasation of leukocytes plays a role and the invention extends to such a use and to the use of the compounds for the manufacture of a medicament for treating such diseases or disorders,
Diseases or disorders of this type include inflammatory arthritis such as rheumatoid arthritis, vasculitis or polydermatomyositis, multiple sclerosis, allograft rejection, diabetes, inflammatory dermatoses such as psoriasis or dermatitis, asthma and inflammatory bowel disease.
For the prophylaxis or treatment of disease the compounds according to the invention may be administered as pharmaceutical compositions, and according to a further aspect of the invention we provide a pharmaceutical composition which comprises a compound of formula (1) together with one or more pharmaceutically acceptable carriers, excipients or diluents.
Pharmaceutical compositions according to the invention may take a form suitable for oral, buccal, parenteral, nasal, topical or rectal administration, or a form suitable for administration by inhalation or insufflation.
For oral administration, the pharmaceutical compositions may take the form of, for example, tablets, lozenges or capsules prepared by conventional means with pharmaceutically acceptable excipients such as binding agents (e.g. pregelatinised maize starch, polyvinylpyrrolidone or hydroxypropyl methylcellulose); fillers (e.g. lactose, microcrystalline cellulose or calcium hydrogen phosphate); lubricants (e.g. magnesium stearate, talc or silica); disintegrants (e.g. potato starch or sodium glycollate); or wetting agents (e.g. sodium lauryl sulphate). The tablets may be coated by methods well known in the art. Liquid preparations for oral administration may take the form of, for example, solutions, syrups or suspensions, or they may be presented as a dry product for constitution with water or other suitable vehicle before use. Such liquid preparations may be prepared by conventional means with pharmaceutically acceptable additives such as suspending agents, emulsifying agents, non-aqueous vehicles and preservatives. The preparations may also contain buffer salts, flavouring, colouring and sweetening agents as appropriate.
Preparations for oral administration may be suitably formulated to give controlled release of the active compound.
For buccal administration the compositions may take the form of tablets or lozenges formulated in conventional manner.
The compounds for formula (1) may be formulated for parenteral administration by injection e.g. by bolus injection or infusion. Formulations for injection may be presented in unit dosage form, e.g. in glass ampoule or multi dose containers, e.g. glass vials. The compositions for injection may take such forms as suspensions, solutions or emulsions in oily or aqueous vehicles, and may contain formulatory agents such as suspending, stabilising, preserving and/or dispersing agents. Alternatively, the active ingredient may be in powder form for constitution with a suitable vehicle, e.g. sterile pyrogen-free water, before use.
In addition to the formulations described above, the compounds of formula (1) may also be formulated as a depot preparation. Such long acting formulations may be administered by implantation or by intramuscular injection.
For nasal administration or administration by inhalation, the compounds for use according to the present invention are conveniently delivered in the form of an aerosol spray presentation for pressurised packs or a nebuliser, with the use of suitable propellant, e.g. dichlorodifluoromethane, trichloro-fluoromethane, dichlorotetrafluoroethane, carbon dioxide or other suitable gas or mixture of gases.
The compositions may, if desired, be presented in a pack or dispenser device which may contain one or more unit dosage forms containing the active ingredient. The pack or dispensing device may be accompanied by instructions for administration.
The quantity of a compound of the invention required for the prophylaxis or treatment of a particular condition will vary depending on the compound chosen, and the condition of the patient to be treated. In general, however, daily dosages may range from around 100 ng/kg to 100 mg/kg e.g. around 0.01 mg/kg to 40 mg/kg body weight for oral or buccal administration, from around 10 ng/kg to 50 mg/kg body weight for parenteral administration and around 0.05 mg to around 1000 mg e.g. around 0.5 mg to around 1000 mg for nasal administration or administration by inhalation or insufflation.
The esters of formula (1) may be prepared by the processes described in the Examples hereinafter. In general this involves esterification of an intermediate acid of formula (2): 
using standard methods known to those skilled in the art, such as reaction with an alcohol of formula R1OH in the presence of an acid catalyst e.g. p-toluenesulfonic acid. Alternatively a condensing agent, for example a diimide such as 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide or N,Nxe2x80x2-dicyclohexylcarbodiimide, may be employed, advantageously in the presence of a catalyst such as a N-hydroxy compound e.g. a N-hydroxytriazole such as 1-hydroxybenzotriazole.
Intermediates of formula (2) may be prepared using methods as described in the Examples hereinafter.
Alternatively an ester of formula (1) may undergo transesterification, preferably in the presence of an acid catalyst, to give another ester of formula (1).
Esters of formula (1) may also be prepared by coupling an amine of formula (3): 
with an activated acid of formula (4): 
The acid of formula (4) may be activated by conversion into an acid chloride, using standard methods known to those skilled in the art, for example, as described in the Examples hereinafter. The coupling reaction may be performed in the presence of a base, such as a hydride, e.g. sodium hydride or an amine, e.g. triethylamine or N-methylmorpholine, in a solvent such as a halogenated hydrocarbon, e.g. dichloromethane or carbon tetrachloride or a dipolar aprotic solvent such as an amide, e.g. dimethylformamide or an ether, e.g. a cyclic ether such as tetrahydrofuran, at for example ambient temperature. Alternatively, the acid of formula (4) may be coupled directly with the amine of formula (3) by the use of a condensing agent, for example a diimide such as 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide or N,Nxe2x80x2-dicyclohexyl carbodiimide, advantageously in the presence of a catalyst such as a N-hydroxy compound e.g. a N-hydroxytriazole such as 1-hydroxybenzotriazole. Alternatively the acid may be reacted with a chloroformate, for example ethylchloroformate, prior to the desired acylation reaction.
Amines of formula (3) may be prepared using the general route as set out in Scheme A below. 
Thus, amines of formula (3) may be prepared by reduction of a nitro compound of formula (5). Suitable conditions may involve catalytic hydrogenation using for example hydrogen in the presence of a metal catalyst, for example palladium on a support such as carbon in a solvent such as an ether, e.g. tetrahydrofuran or an alcohol e.g. methanol or ethanol. The reaction may be performed at atmospheric pressure or up to a pressure of 100 ps.i. Alternatively chemical reduction using for example a metal, e.g. tin or iron, in the presence of an acid such as hydrochloric acid may be employed.
Nitro compounds of formula (5) may be prepared by reaction of a cyclobutadiene of formula (7) with an amine of formula (6). The reaction may be performed in an inert solvent or mixture of solvents, for example a hydrocarbon such as an aromatic hydrocarbon e.g. benzene or toluene and/or a halogenated hydrocarbon such as 1,2-dichloroethane, or dichloromethane at a temperature from 0xc2x0 C. to the reflux temperature. Where necessary, for example when a salt of an amine of formula (6) is used, an organic base such as diisopropylethylamine can be added.
Amines of formula (6) may be prepared using standard methods known to those skilled in the art, such as esterification of commercially available 4-nitrophenylalanine.
Intermediates of formula (7) may be prepared using methods as described in International Patent Application WO 02/068393.
In addition, N-oxides of compounds of formula (1) may be prepared for example by oxidation of the corresponding nitrogen base using an oxidising agent such as hydrogen peroxide in the presence of an acid such as acetic acid, at an elevated temperature, for example around 70xc2x0 C. to 80xc2x0 C., or alternatively by reaction with a peracid such as peracetic acid in a solvent, e.g. dichloromethane, at ambient temperature.
Salts of compounds of formula (1) may be prepared by reaction of a compound of formula (1) with an appropriate acid in a suitable solvent or mixture of solvents e.g. an organic solvent such as an ether e.g. diethylether, or an alcohol, e.g. ethanol using conventional procedures.
Where it is desired to obtain a particular enantiomer of a compound of formula (1) this may be produced from a corresponding mixture of enantiomers using any suitable conventional procedure for resolving enantiomers.
Thus for example diastereomeric derivatives, e.g. salts, may be produced by reaction of a mixture of enantiomers of formula (1) e.g. a racemate, and an appropriate chiral compound, e.g. a chiral base. The diastereomers may then be separated by any convenient means, for example by crystallisation and the desired enantiomer recovered, e.g. by treatment with an acid in the instance where the diastereomer is a salt.
In another resolution process a racemate of formula (1) may be separated using chiral High Performance Liquid Chromatography. Alternatively, it desired a particular enantiomer may be obtained by using an appropriate chiral intermediate in one of the processes described above. Alternatively, a particular enantiomer may be obtained by performing an enantiomer specific enzymatic biotransformation e.g. an ester hydrolysis using an esterase and then purifying only the enantiomerically pure hydrolysed acid from the unreacted ester antipode.
Chromatography, recrystallisation and other conventional separation procedures may also be used with intermediates or final products where it is desired to obtain a particular geometric isomer of the invention.
The following Examples illustrate the preparation of compounds of the invention. All temperatures are in xc2x0 C. The following abbreviations are used:
EtOAcxe2x80x94ethyl acetate;
DCMxe2x80x94dichloromethane;
MeOHxe2x80x94methanol;
HOAcxe2x80x94acetic acid;
EtOHxe2x80x94ethanol;
Mexe2x80x94methyl;
DMSOxe2x80x94dimethylsulphoxide;
DMFxe2x80x94N,N-dimethylformamide;
THFxe2x80x94tetrahydrofuran,
HOBTxe2x80x941-hydroxybenzotriazole
Et3NHClxe2x80x94triethylamine hydrochloride
EDCxe2x80x941-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride All NMR""s were obtained either at 300 MHz or 400 MHz.
All Intermediates and Examples were named with the aid of Beilstein Autonom (available from MDL Information Systems GmbH, Therdor-Heuss-Allee 108D 60486, Frankfurt, Germany) or were given names that seemed consistent.
Intermediate 1
3-Cyano-4-(2-(N,N-dimethylamino)ethylen-1-yl)pyridine
A solution of 4-methyl-3-cyanopyridine [prepared according to Ref: J. Prakt. Chem. 338, 663 (1996)], (8.0 g, 67.8 mmol) and N,N-dimethylformamide diethyl acetal (11.0 g, 74.8 mmol) in dry DMF (50 ml) was stirred at 140xc2x0 under N2 for 2 days. An additional portion of N,N,-dimethylformamide diethyl acetal (5 g) was added and stirred at 140xc2x0 for 4 h. The volatiles were removed in vacuo and the obtained dark oil partitioned between EtOAc (300 ml) and water (50 ml). The phases were separated and the aqueous layer re-extracted with EtOAc (3xc3x97100 ml). The combined organic extracts were washed with brine (30 ml), dried (Na2SO4), treated with activated charcoal, filtered and evaporated in vacuo to afford essentially pure title compound as a dull orange solid (10.1 g, 85%). xcex4H (CDCl3) 8.49 (1H, s), 8.25 (1h, d, J 5.9 Hz), 7.29 (1H, d J 13.2 Hz), 7.09 (1H, d, J 5.9 Hz), 5.25 (1H, d, J 13.2 Hz) and 2.99 (6H, s); m/z (ES+, 70V) 174 (MH+).
Intermediate 2
1-Hydroxy-[2,7]-naphthyridine Hydrochloride Salt
HCl gas was bubbled through a stirred solution of Intermediate 1 (6.2 g, 3.58 mmol) in glacial acetic acid (50 ml) and water (0.64 ml, 3.55 mmol) for 1-2 min. The reaction mixture was stirred in a stoppered flask at 40xc2x0 for 18 h. The volatiles were removed in vacuo affording a dark residue, which was treated with water (3xc3x9720 ml) and re-evaporated in vacuo. The obtained dark semi-solid was treated with 40 ml warm ethanol, ice-cooled, and the undissolved solid collected by filtration affording the title compound as a green coloured solid (5.2 g, 80%). xcex4H (DMSO-d6) 12.5 (1H, br s), 9.38 (1H, s), 8.84 (1H, d, J 7.0 Hz), 8.15 (1H, d, J 7.0 Hz), 7.89 (1H, br dd, J 7.0, 5.0 Hz) and 6.85 (1H, d, J 7.0 Hz); m/z (ES+, 70V), 147 (MH+).
Intermediate 3
1-Chloro-[2,7]-naphthyridine
Intermediate 2 (5.2 g, 28.5 mmol) was stirred with phosphorous oxychloride (75 ml) at 110xc2x0 for 24 h. The volatiles were removed in vacuo affording a dark oil which was poured into an ice-bath cooled mixture of saturated aqueous NaHCO3 (100 ml containing 20 g solid NaHCO3) and EtOAc (100 ml). After thorough mixing the phases were separated and the aqueous layer re-extracted with EtOAc (2xc3x9775 ml). The combined organic extracts were washed with brine (15 ml), dried (Na2SO4) and evaporated in vacuo to afford the title compound as a yellow solid (4.0 g, 85%). xcex4H (CDCl3) 9.45 (1H, s), 8.81 (1H, d, J 5.7 Hz), 8.47 (1H, d, J 5.7 Hz), 7.66 (1H, d, J 5.7 Hz) and 7.60 (1H, d, J 5.7 Hz); m/z (ES+, 70V) 165 and 167 (MH+).
Intermediate 4
Ethyl (2S)-2-amino-3-[4-([2.7]naphthyridin-1-ylamino)phenyl]propanoate
A solution of ethyl-(S)-3-[4-aminophenyl]-2-[t-butoxycarbonylamino]propanoate (638 mg, 2.07 mmol) and Intermediate 3 (310 mg, 1.88 mmol) in ethoxyethanol (2 ml) was stirred at 120xc2x0 for 15 min and at 100xc2x0 for 1 h under nitrogen. The volatiles were removed in vacuo and the dark residue partitioned between EtOAc (70 ml) and saturated aqueous NaHCO3 (10 ml). The phases were separated and the aqueous layer re-extracted with EtOAc (2xc3x9730 ml). The combined organic extracts were washed with brine (10 ml), dried (Na2SO4) and evaporated in vacuo to afford a dark foam. Chromatography (SiO2; 5 to 10% MeOH/DCM) afforded a mixture of ethyl-(S)-3-[4-([2,7]naphthyridin-1-ylamino)phenyl]-2-[(t-butoxycarbonyl)amino]propanoate and some of the title compound (730 mg). This mixture was treated with a solution of trifluoroacetic acid (5 ml) and DCM (5 ml) at room temperature for 1 h. The volatiles were removed in vacuo and the residue partitioned between EtOAc (75 ml) and saturated aqueous NaHCO3 (20 ml). The phases were separated and the aqueous layer re-extracted with EtOAc (3xc3x9730 ml). The combined organic extracts were washed with brine (10 ml), dried (Na2SO4) and evaporated in vacuo to afford an orange solid. Chromatography (SiO2; 10% MeOH/DCM) afforded the title compound as a straw-coloured solid (420 mg, 60% over two steps). xcex4H (CDCl3) 10.70 (1H, s), 10.31 (1H, s), 9.44 (1H, d, J 5.6 Hz), 8.94 (1H, d, J 5.6 Hz), 8.55 (1H, d, J 7.3 Hz), 8.54 (2H, d, J 8.5 Hz), 8.46 (1H, d, J 5.6 Hz), 7.94 (2H, d, J 8.5 Hz), 4.84 (2H, q, J 7.1 Hz), 4.35 (1H, t, J 6.6 Hz), 4.10 (2H, br s), 3.64 (1H, dd, J 13.5, 6.4 Hz), 3.56 (1H, dd, J 13.5, 7.0 Hz) and 1.95 (3H, t, J 7.1 Hz); m/z (ES+, 70V) 337 (MH+).
Intermediate 5
Ethyl (2S)-3-[4-([2,7]naphthyridin-1-ylamino)phenyl]-2-(3-oxospiro[3.5]non-1 en-1-ylamino)propanoate
A solution of the ethyl ester of Intermediate 4 (565 mg, 1.68 mmol) and 1-keto-3-hydroxyspiro[3,5]-non-2-ene [prepared according to the method of Wasserman, H. H et al J. Org. Chem., 38, 1451-1455 (1973)] (280 mg, 1.84 mmol) in DCM (20 ml) was stirred at room temperature for 24 h. Concentration in vacuo and chromatography (SiO2, EtOAc) of the residue gave the title compound as a pale yellow powder (1.4 mmol, 73%). xcex4H (CDCl3) 9.61 (1H, s), 8.65 (1H, d, J 5.7 Hz), 8.25 (1H, d, J 5.8 Hz), 7.71 (2H, d, J 8.4 Hz), 7.63 (1H, d, J 8.5 Hz), 7.12 (2H, d, J 8.5 Hz), 7.05 (1H, d, J 5.8 Hz), 5.80 (1H, m), 4.55 (1H, s), 4.29 (2H, q, J 7.2 Hz), 3.13 (2H, m), 1.87-1.25 (14H, m); m/z (ES+, 70V) 471.1 (MH+).
Intermediate 6
Ethyl (2S)-2-(2-bromo-3-oxospiro[3.5]non-1-en-1-ylamino)-3-[4-([2.7]naphthyridin-1-ylamino)phenyl]propanoate
A stirred solution of the compound of Intermediate 5 (300 mg, 0.637 mmol) and triethylamine (1.2 eq, 100 xcexcl) in THF (10 ml) at 0xc2x0 was treated dropwise with a solution of bromine in DCM (2% v/v, 2.1 ml, 1.2 eq). After 12 h the reaction was diluted with DCM (50 ml) and washed successively with saturated aqueous NaHCO3, dried (MgSO4) filtered and concentrated in vacuo. The residual foam was triturated with diisopropylether and the resulting solid collected and dried in vacuo to give the title compound as a pale yellow powder (0.45 mmol, 76%). xcex4H (CDCl3) 9.81 (1H, s), 8.64 (1H, d, J 5.7 Hz), 8.29 (1H, d, J 5.8 Hz), 7.75 (2H, d, J 8.3 Hz), 7.60 (1H, d, J 5.8 Hz), 7.12 (2H, d, J 8.4 Hz), 7.08 (1H, d, J 5.7 Hz), 5.91 (1H, m), 5.03 (1H, m), 4.28 (2H, q, J 7.1 Hz), 3.29 (2H, m), 1.81-1.39 (10H, m), 1.35 (3H, t, J 7.1 Hz); m/z (ES+, 70V) 550.0 (MH+).
Intermediat 7
(2S)-2-(2-Bromo-3-oxospiro[3.5]non-1-en-1-ylamino)-3-[4-([2.7]naphthyridin-1-ylamino)phenyl]propionic acid
The compound in Intermediate 6 (219 mg, 0.40 mmol) in THF (5 ml) was treated in a single portion with LiOH.H2O (19 mg, 0.44 mmol) in H2O(1 ml) and the reaction stirred at room temperature for 2 h. The reaction was then quenched by the addition of HOAc (glacial, 1 ml) and the volatiles removed in vacuo. Water (10 ml) was then added to the residual foam and stirred vigorously to effect precipitation. The precipitate was then collected by vacuum filtration and the residue washed with water (2xc3x975 ml). Drying under vacuum gave the title compound as a white powder (0.25 mmol, 64%). xcex4H (DMSO d6, 300 K) 9.90 (1H, s), 9.56 (1H, s), 8.86 (1H,d, J 9.3 Hz), 8.66 (1H, d, J 5.6 Hz), 8.17 (1H, d, J 5.7 Hz), 7.81 (2H, d, J 8.2 Hz), 7.70 (1H, d, J 5.6 Hz), 7.24 (2H, d, J. 8.4 Hz), 7.14 (1H, d, J 5.7 Hz), 4.78 (1H, m) 3.23 (1H, dd, J 13.9, 4.1 Hz), 2.99 (1H, dd, J 13.7, 10.0 Hz), 1.81-1.04 (11H, m); m/z (ES+, 70V) 522.0 (MH+).